TDO2 and neoplasm: To assess whether IDO1 and TDO2 were indeed associated with AHR activity,3 Opitz et al. performed the high or low group of IDO1 or TDO2 expression and weighted gene co-expression network analysis (WGCNA) across the 32 TCGA tumor entities and found that there was a positive correlation between IDO1 or TDO2 and AHR signaling in 23 tumor types.